The etiology and prevention of drug abuse in adolescents and young adults is complex, requiring both depth and breadth of understanding. Substantially improving this understanding is a challenge because the processes underlying drug abuse and its prevention occur across multiple levels of analysis, ranging from the individual level (e.g., cognitive and affective factors) to the peer group level (e.g., social network influences) to the larger societal level (e.g., cultural influences). A combination of theoretical approaches and research methods from multiple scientific disciplines is necessary to address such a complex array of causal factors. Further, specific strategies of cross-fertilization need to be in place to integrate multiple disciplines and levels effectively, to encourage a synthesis of understanding. The proposed Transdisciplinary Prevention Research Center (TPRC) will integrate strategies and theories from multiple scientific disciplines to gain a more complete, comprehensive understanding of the cognitive, affective, social, and cultural influences on drug abuse and its prevention among adolescents and young adults. Three distinct but interrelated research projects will advance this effort from the perspectives of memory and implicit cognition, affective pathways, social network effects, and cultural contextual effects. Three cores will facilitate high-quality, integrative training, administrative coordination, and data analysis for all USC TPRC personnel. The research in this TPRC focuses on the themes of multiple levels of analysis and change within a cross-cultural context. One of the projects focuses specifically on issues of culture and acculturation, and the other two projects will involve culturally diverse samples.